Microencapsulated gardenia yellow pigment and a preparation method thereof

A method for preparing a microencapsulated gardenia yellow pigment, characterized in that the microencapsulated gardenia yellow pigment is prepared by the following steps:

• S1, under nitrogen protection, according to a mass ratio of 1:3.8˜4.1:0.08˜0.09:0.06˜0.08, adding pre-treated polyethylene glycol monomethyl ether, vinylpyridine, benzoyl peroxide, and cuprous bromide to methanol, after stirring evenly, freeze-drying by using liquid nitrogen, following by 2˜3 cycles of defrosting with nitrogen gas, stirring for 25˜35 minutes at 25˜30° C., then raising a temperature to 55˜65° C. and reacting for 8˜12 hours, after reaction, adding the pre-treated polyethylene glycol monomethyl ether to tetrahydrofuran, stirring evenly and stopping reaction, passing through an alumina chromatography column to remove copper ions, then concentrating to obtain a precipitate by using rotary evaporation, after concentration, adding n-hexane to the precipitate, after standing and precipitating, filtering and vacuum drying to obtain a preliminary co-encapsulation polymer;
• S2, under nitrogen protection, adding the preliminary co-encapsulation product, modified methyl methacrylate, benzoyl peroxide, and cuprous bromide to methanol according to a mass ratio of 1:24˜26:1.8˜2.2:0.15˜0.18, stirring evenly, freeze-drying by using liquid nitrogen, following by nitrogen gas defrosting 2˜3 times, stirring for 25˜35 minutes at 25˜30° C., then raising a temperature to 55˜65° C. and reacting for 8˜12 hours, after reaction, adding 3˜4 times a mass of the preliminary co-encapsulation product in tetrahydrofuran solution to dilute, stirring evenly and stopping reaction, passing through an alumina chromatography column to remove copper ions, then concentrating by using rotary evaporation to obtain a precipitate, after concentration, adding n-hexane to the precipitate, after standing and precipitating, filtering and vacuum drying to obtain a co-encapsulation polymer;
• and
• S3, adding the co-encapsulation polymer to dichloromethane according to a mass ratio of 1:50˜60, stirring to dissolve, and then adding 0.6˜0.8 times a mass of the co-encapsulation polymer in gardenia yellow pigment, ultrasonically dispersing for 20˜25 minutes to prepare an oil phase, at a temperature of 25˜30° C., adding the oil phase to an aqueous phase in a volume ratio of 1:1, stirring for 3˜5 minutes at a speed of 1800 rpm, then stirring for 4˜6 hours at a speed of 600 rpm, after standing to evaporate dichloromethane, performing ultrafiltration and centrifugation, washing with deionized water 2˜3 times, then freeze-drying to obtain the microencapsulated gardenia yellow pigment.